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content / browser / metrics / histograms_monitor.h [blame]
// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CONTENT_BROWSER_METRICS_HISTOGRAMS_MONITOR_H_
#define CONTENT_BROWSER_METRICS_HISTOGRAMS_MONITOR_H_
#include <map>
#include <string_view>
#include "base/metrics/histogram_samples.h"
#include "base/metrics/statistics_recorder.h"
#include "content/common/content_export.h"
namespace content {
// This class handles the monitoring feature of chrome://histograms page,
// which allows the page to be updated with histograms logged since the
// monitoring started.
//
// Note that this class does not handle merging histograms from any
// |HistogramProvider| instances. It also does not handle synchronizing
// histograms from subprocesses. The caller has the responsibility for these
// beforehand.
class CONTENT_EXPORT HistogramsMonitor {
public:
HistogramsMonitor();
~HistogramsMonitor();
HistogramsMonitor(const HistogramsMonitor&) = delete;
HistogramsMonitor& operator=(const HistogramsMonitor&) = delete;
// Fetches and records a snapshot of the current histograms, as the baseline
// to compare against in subsequent calls to GetDiff().
void StartMonitoring(std::string_view query);
// Gets the histogram diffs between the current histograms and the snapshot
// recorded in StartMonitoring().
base::Value::List GetDiff();
private:
// Gets the difference between the histograms argument and the stored snapshot
// recorded in StartMonitoring().
base::Value::List GetDiffInternal(
const base::StatisticsRecorder::Histograms& histograms);
std::string query_;
std::map<std::string, std::unique_ptr<base::HistogramSamples>>
histograms_snapshot_;
};
} // namespace content
#endif // CONTENT_BROWSER_METRICS_HISTOGRAMS_MONITOR_H_